The obvious one for the ground cover would be HC, some crpyts & blxya for the bushes on the right side. Even some aquatic ferns would do well. Then some taller stem's like Rotolas, ludwiga's for the far back right.
I would try Pogostemon Helferi, Hemianthus Micranthemoides and Rotala Sp. Green for the right side front, either HC or Utricularia Graminifolia for the track, and then perhaps Tonina Fluviatilis for the rear cedars.
I like crypts, HM, and maybe Tonina Belem for the bushy right side. Perhaps even some Rotala sp. green. Ground cover - HC. The idea of Tonia fluviatilis for the trees is a neat idea. or maybe get some wood and tie some moss (Xmas, willow, java) to the top and let it grow out to form a tree top.
Thanks for the advice. I think I'll make the tree's from christmas moss and driftwood. Green rotala should work well for the right side. Tonina's seem like they are way too difficult for me to want to deal with. Pogostemon helferi looks like it would be a good plant to also put on the right side. I hadn't heard of it before, but it looks nice. HM on the right side would probably look nice as well, and then HC for the ground cover.
If you want to recreate the look of the forest ferns in the photo, I would use Bolbitis and Ceratopteris, as these are the most frilly looking aquatic ferns and the easiest to grow. Hygrophila difformis and balsimica also have that type of look.
I don't see how Rotala and particularly Tonina give you that forest type look. Hygrophila corymbosa kompakt would give you a nice mid level "bush" and i think the shape of it would fit in with what you are trying to create. Hygrophila corymbosa angustifolia is a tall plant with very thin long leaves like a willow tree. That might work next to your wood/moss trees.